This invention relates generally to cutting tools, and more particularly to a coping saw assembly.
Carpenters have traditionally used coping saws to cut the joints between crown moulding, chair rails, and other forms of wood and composite moulding. A traditional coping saw is a hand saw having a narrow fixed blade held in tension by a generally rectangular- or square-shaped frame. The depth of the frame provides considerable clearance relative to the fixed saw blade to enable to the saw to be manipulated to cut curves or sharp-angled cuts in wood and other products. Sawing with a traditional coping saw can be slow, arduous, and labor intensive depending on the scope of the project. The operator moves the saw back and forth monitoring the blade to be sure the cut is along the desired curve.
To expedite the coping process, others have attempted to mechanize the tool. For example, the reader is referred to U.S. Pat. Nos. 5,388,334; 5,363,558; 5,220,729; 3,621,894 and 1,955,063. Problems exist with substantially all of the foregoing designs. An important disadvantage associated with the prior saws is they fail to take into account how coping saws are used by the operator. Traditionally, manual coping saws are used to cut complicated curves and profiles. The operator cuts along a first line, backs out, and then approaches the cut from a different angle. The prior powered coping saws made it difficult for the operator to readily back out of the cut and reposition the saw for the different angle. More importantly, the prior saws were clumsy and cumbersome designs requiring the operator to perform athletic maneuvers to position the saw to make the right cut. In versions where the blade reciprocates, it would be difficult to maintain the position of the saw because the force generated by the blade would tend to make the saw chatter and move the operators hand rather than the blade through the workpiece. In substantially all of the prior power coping saw designs, the drive and track systems were complicated and expensive to manufacture.
The instant invention provides a solution to substantially all of the difficulties presented by the prior devices, in that it is easy for the operator to grip and maneuver for different cuts, it is mechanically easy to build, and relatively inexpensive to manufacture.
The instant invention is a unique mechanized coping saw which provides maximum flexibility to quickly, easily, and accurately cut (cope) a workpiece such as a piece of moulding. In general, the instant invention provides a continuous loop blade disposed between two pulleys which provides two generally parallel and spaced apart saw-blade cutting sections, each traveling in an opposite direction of the other so the user can select the best cutting direction and angle to complete the cut. The instant invention also provides a unique system for retaining the blade on the two pulleys, resulting in a more accurate and reliable blade.
In one form of the invention, the coping saw includes a frame internal to a housing which supports a drive pulley at one end, and a driven pulley at an opposite end. The frame is shaped such that a bridge defines a space between the two pulleys. A continuous loop blade is mounted on the two pulleys such that two blade segments span the space between the pulleys, both blade-segments available to cut the work piece at the election of the operator.
In another form of the invention, the coping saw comprises a housing which provides the framework and support for the spaced-apart drive pulley and driven pulley. The continuous loop blade is mounted at least partially circumferentially around the spaced-apart drive pulley and driven pulley. The drive and driven pulleys each have a circumferential groove for partially receiving a polymeric O-ring or band used to provide traction and tracking of the continuous loop blade around the pulleys.
In another form of the invention, the housing containing the saw provides a work space intermediate the first and the second ends of the housing. It is across this work space that the two continuous blade sections traverse between the two pulleys, providing two cutting sections of blade moving in opposite directions. The availability of the two cutting sections moving in opposite directions provides the operator greater flexibility in cutting options to cope a desired profile.
In yet another form of the invention, the mechanized saw includes a housing having a first and second spaced-apart end portions interconnected by a bridge which defines a C-shaped transverse channel extending between the first and second end portions. The first and second end portions and the bridge are aligned along a first plane of symmetry which includes a longitudinal axis for the housing. A motor is provided in the first end portion of the housing and has a shaft extending from at least one end thereof, the longitudinal axis of which is contained in the first plane of symmetry. A drive pulley is provided in the first end portion of the housing and mounted to the free end of the shaft extending from the motor. The drive pulley is oriented such that it is contained in a plane of symmetry different from, and preferably perpendicular to, the first plane. A carriage is provided in the second end portion of the housing and is configured to be movable between a first and a second position. A driven pulley is mounted on the carriage such that the drive pulley and the driven pulley are approximately contained in the same plane of symmetry. A continuous loop blade is then mounted on the drive pulley and the driven pulley such that first and second sections of the blade span the C-shaped channel at spaced-apart locations. Blade guides are provided in the housing adjacent the transverse channel to provide lateral stiffness and stability to the two blade sections. The drive and driven pulleys rotate the blade, where a first section of the blade moves in one direction opposite to that of the second section of the blade such that both sections of the blade provide opposite cutting actions.
In a further form of the invention, the drive pulley and the driven pulley are slightly misaligned or offset from the second plane of symmetry to assist in tracking and/or retaining the continuous loop blade on the two pulleys. The resulting arrangement of the two offset pulleys, in effect creates a bisected hyperbola which, upon rotation, assists in the tracking of the continuous loop blade on the two pulleys.
In yet another form of the invention, the drive pulley and driven pulley are mounted on a frame by one or more bearings. At least one of the pulleys, and preferably the driven pulley, is mounted to an adjustable carriage which in turn is fixed to the frame-adjustment being provided by a threaded member. The drive pulley includes a shaft extending therefrom which is receivable in a chuck of a power tool selectively coupled and uncoupled with respect to the frame. In this fashion the invention could be in the form of attachment for a conventional power tool such as drill.
In still a further embodiment of the invention, outrigger and guide rollers would be disposed intermediate the drive pulley and the driven pulley to improve tracking of the continuous loop blade about the pulleys, and to increase blade life as the blade does not encounter a rapid bending moment produced by the radius of the pulley. Rather the outrigger rollers provide a gradual feed to the drive and driven pulleys.
In one other form of the invention, the body or housing for the saw may be laterally offset such that the depth of the C-shaped work area is increased. However, in this embodiment, it is envisioned that the lateral offset of the housing will enclose one of the two exposed blade segments. In this configuration, although the parts and components are substantially similar, one of the blades is within the housing, providing a skiving saw or draw saw.
In yet another form of the invention, a polymeric housing is provided which is formed in a manner to provide an intermediate space between two ends of the housing. In one end of the housing, a motor (either electric or air) is provided which is coupled by a shaft to a drive pulley. The other end of the housing contains a carriage which in turn is coupled to and support a driven pulley. In this embodiment, the carriage is adjusted by an over-center lever to move the carriage between a first and second positions. Mounted at least partially around each of the drive and driven pulleys is a continuous-loop saw blade which spans at two spaced apart locations the intermediate space defined between the two ends of the housing. Guide rollers are provided adjacent the intermediate space in a manner to lie adjacent the continuous-loop saw blade to provide support and to reduce the chance the saw blade will come off the drive and driven pulleys during operation. In particular, the guide rollers include at least one anti-backout bearings adjacent each saw-blade section and disposed adjacent the cutting edge of the saw blade to keep the saw blade tracking on the drive and driven pulleys during operation.
The instant mechanism described and claimed herein provides the woodworker substantial artistic flexibility and reliability in a powered saw. Two saw-blade sections, rather than one saw blade, travel in opposite directions so that the operator may elect to one or the other to complete a complex cope. Additionally, substantial strength and alignment is provided to the blades by the guide and support bearings located adjacent the C-shaped channel and the blade. Together with the guide bearings, the two blade segments are adequate to cut soft and hard woods alike in a fraction of the time of conventional coping saws.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.